The present invention relates to a hydrogen storage element made of a complex substance chiefly containing carbon which is a light material for storing hydrogen gas, and also relates to a manufacturing method for fabricating the same.
Hydrogen gas is an excellent clean energy source because it produces no harmful emission, such as nitrogen oxide or carbonic acid gas, and is free from the so-called green house effect. Furthermore, in view of the difficulty in storing electric energy, surplus electric energy of night time is used for the electrolysis of water and stored in the form of hydrogen gas. Thus, hydrogen gas has an important role in the present and future energy cycle.
To realize a rapid and marvelous progress in the field of hydrogen utilizing technologies, such as hydrogen fuel cars, a key factor is to provide a safe and light hydrogen storing element and its manufacturing method.
An object of the present invention is to provide a safe, light-weight, easily portable, and low-pressure hydrogen storing element and its manufacturing method.
In order to accomplish the above and other related objects, one aspect of the present invention provides a hydrogen storage element comprising a tubular graphite body forming an elongated shell of the hydrogen storage element, at least one metal plug closing an open end of the elongated shell so as to form a closed inside space for storing hydrogen gas.
Preferably, the closed inside space is partitioned into a plurality of independent spaces by metal particles.
To obtain excellent hydrogen storage capability, it is preferable that the closed inside space has a diameter in a range from 0.2 nm to 100 nm and a length in a range from 100 nm to 100 xcexcm.
Preferably, the metal plug contains a metallic component selected from the group consisting of nickel, cobalt, iron, palladium and their alloys, because the hydrogen gas can easily penetrate these metal materials and these metal materials can be firmly connected to the carbon of the tubular graphite body.
Preferably, the tubular graphite body is multilayered graphite sheets forming a cup-shaped shell having an open end closed by the metal plug.
Another aspect of the present invention provides a manufacturing method of a hydrogen storage element comprising the steps of placing a material of a metal-containing compound in a closed chamber, and heating the material so that the evaporate material decomposes at a selected temperature in a range from 550xc2x0 C. to 950xc2x0 C., thereby forming a tubular graphite body.
Preferably, the metal contained in the material is selected from the group consisting of nickel, cobalt, iron, palladium and their alloys.
Preferably, the closed chamber is vacuumized, or filled with an inert or reducing gas.
Another aspect of the present invention provides a manufacturing method of a hydrogen storage element comprising the steps of putting a material of a metal-containing compound in a quartz boat, placing the quartz boat in a quartz reaction tube having an open end, airtightly closing the open end of the quartz reaction tube and vacuumizing an inside space of the quartz reaction tube, and heating the material so that evaporate material decomposes at a selected temperature in a range from 550xc2x0 C. to 950xc2x0 C., thereby forming an elongated tubular graphite body with one end closed by a metallic plug.
Preferably, a first heating device is provided for evaporating the material and a second heating device is provided for decomposing the evaporated material, and the first and second heating devices are arranged in a row along an elongated body of the quartz reaction tube.
Preferably, the quartz boat is placed at a portion corresponding to the first heating device. The second heating device preheats the quartz reaction tube at a portion offset from the quartz boat at the selected temperature before the first heating device is activated to heat the material.
Another aspect of the present invention provides a manufacturing method of a hydrogen storage element comprising the steps of placing a material of a metal-containing compound in a closed chamber, heating the material so that evaporate material decomposes at a selected temperature in a range from 550xc2x0 C. to 950xc2x0 C., thereby fabricating a tubular graphite body, and mechanically cracking the fabricated tubular graphite body.